This invention relates to gate valves and more particularly to gate valves of the expanding type comprising a valve assembly having a gate and segment which expand at fully opened and closed positions.
Heretofore, as shown in U.S. Pat. No. 3,893,652 dated July 8, 1975 expanding gate valve structures have been provided which include a gate and a segment carried by the gate with the gate and segment having opposed interfitting V-shaped faces. With the gate and segment each having a single interfitting V-shaped face, a relatively large thickness of the valve assembly is necessary to provide the V-shaped recess. Also, during movement between open and closed positions, a pre-expansion of the gate and segment might occur which will increase the operating torque required for moving the valve between open and closed positions. While a spring is shown in U.S. Pat. No. 3,893,652 to hold the gate and segment together, the spring must be tightly stressed in order to hold the gate and segment together during travel as a relatively small angle (between around 12.degree. and 18.degree. ) is provided by the V-shaped faces relative to the direction of travel of the gate assembly between opened and closed positions.
Any pre-expansion of the gate and segment during travel is highly undesirable as binding against the adjacent seats and possible jamming of the valve assembly may occur.